Modern x-ray fluoroscopic/radiographic imaging systems include means for operating in a plurality of imaging modes. Such systems, sometimes called "x-ray suite", include a radiation source, which directs x-rays through a patient onto the input face of an image intensifier tube. The image intensifier tube converts a relatively large area of x-rays to a smaller, relatively bright visual image corresponding to the x-ray pattern emerging from the patient. A television camera views an output image from the image intensifier tube and produces a video output comprising an ensemble of signals, including video and appropriate sync signals, which collectively define the viewed pattern, and is known as a composite video signal.
The video signal from the television can be directly coupled to a viewing monitor which produces a visible image corresponding to that viewed by the television camera. Alternately, the video can be directed to various display processing components, such as digital acquisition systems and video tape or video disk recorders. Such devices store and/or process the video signals and playback the video signals to the monitor at a later time.
Such x-ray fluoroscopic/radiographic imaging systems include a "system controller" actuable by an operator to determine the mode in which the x-ray imaging system will operate. There are several such possible operating modes. In fluoroscopy, for example, the video from the camera is transmitted directly to the monitor for real time viewing. There are at least two types of fluoroscopic imaging, i.e., the standard mode and the high resolution mode. The standard mode employs a 525 line per screen image, while the high resolution mode employs a 1049 line image.
In another mode, video from the camera can be directed to a digital acquisition system for storage and later playback. In this mode, the digital acquisition system (DAS) digitizes the information, which is later reconverted to analog form for presentation to the monitor for the production of a viewable image.
In still another mode, video is directed for recording on tape or disc, for later playback. Upon playback, the tape or disc is rerun and a video output is directed to the monitor which produces the viewable image.
A problem which has arisen in operation of these multimode systems or suites is that the various modes of imaging impose different requirements on the viewing monitor for optimal imaging. This multiplicity of monitor requirements has necessitated either the provision of multiple monitors in such x-ray systems, one preset for each mode requiring different performance, or made necessary manual adjustment of a monitor prior to each change in imaging mode.
Parameters of monitor operation which must change for different operating modes are the line scan rate of the image, the aspect ratio of the image, the brightness of the image, and a time constant or delay imposed by the video input circuitry of the monitor on incoming video signals.
As mentioned above, in fluoroscopy, it is often necessary to change between 525 line and 1049 line display formats. Brightness adjustment must be made as a function of which line rate is selected. In fluoroscopy, a 1:1 aspect ratio is desirable.
Where the digital acquisition system is used as a display source, playing back reconverted digital information to the monitor for imaging, the aspect ratio of the monitor-produced image must be changed from 1:1 to 4:3. As in the case of fluoroscopy, either a 525 line or 1049 line display can be selected, depending on the degree of resolution desired. Monitor brightness must be adjusted for each change in line rate and in aspect ratio.
Where a video tape recorder or video disk recorder is used as a display source for the monitor, again, either a 525 line or 1049 line display format can be selected, depending on the degree of resolution desired. Brightness of the monitor must be adjusted as a function of the line rate. The desirable aspect ratio for modes using the video recorders as display sources is 1:1, and, if that aspect ratio represents a change, brightness must be adjusted accordingly with that variable as well. In addition, where a video recorder is used as a display source, a time delay imposed by the input circuitry of the monitor should be decreased to facilitate the display of a stable image.
In the past, these various requirements have been satisfied by the inclusion, with an x-ray system or suite, of multiple monitors, each being preset for operation in accordance with one or another of the various combinations of parameters which are called for for each of the operating modes.
For example, one system uses one monitor to display continuous fluoroscopy, an additional monitor to display images from a digital acquisition system used as a display source, and a third monitor for video recorder output. These monitors, sometimes different in size and brand, add to the cost of the system, can distract the operator by their complexity, and generally complicate the viewability of the diagnostic information. The combination of several monitors also can create a perception that a system is not well integrated due to a number of "add-ons".